Orthogonally-optimized vibration isolation

ABSTRACT

A vibration isolation device for optimally decoupling shear forces that are orthogonal to the principal direction of isolation from microvibrations. A pivoting load support element is free to pivot about a pivot point in response to shear forces, with optimal isolation from coupling to the principal direction of vibration isolation. A friction free bearing for small motion is provided to respond to the forces perpendicular to the principal direction of vibration isolation. An internal load support plate associated with the pivoting element is supported by equalizing springs and is damped by an active actuator driven according to a sensor on the internal load support plate. Adjustment points, such as screws, adjust the pivoting element with respect to the fixed pivot point.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional application of U.S. patent applicationSer. No. 16/010,525, filed Jun. 18, 2018, entitled“Orthogonally-optimized vibration isolation”, the priority of which ishereby claimed.

FIELD

The present invention relates to vibration isolation and, moreparticularly, to vibration-isolation apparatus orthogonally configuredto maximize decoupling and optimize performance of active vibrationisolation in each degree of freedom, for the disturbances coming fromthe floor to the isolated device or from the device coming to the floor.

BACKGROUND

Apparatus for isolating a stationary payload object from vibration(particularly a delicate object such as a measurement instrument orprecision fabrication device) typically is designed to isolate theobject from vibration in more than one axis. In real applications,however, it has proved to be difficult to buildwell-orthogonally-decoupled multi-axis vibration suppression systems.The issue is even more significant when isolating larger systems, wheremore than one actuator is needed to compensate for vibrationaldistortion in multiple axes. Cross-talk between axes significantlydegrades performance of each actively controlled axis, and can oftencompromise feedback control loop stability. Equally or even moredifficult is to actively reduce vibration generated by device and goingfrom that device to the floor (pumps, compressors, moving stages). It istherefore advantageous and desirable to have apparatus which optimizesvibration isolation along single principal direction, while optimallydecoupling vibrational modes orthogonal to that direction. This goal isattained by embodiments of the present invention.

SUMMARY

Embodiments of the present invention provide apparatus for vibrationisolation in a principal direction, in a manner that is optimallydecoupled from vibration that is orthogonal to the direction.

According to various embodiments of the present invention, cross-axisdecoupling is accomplished by providing a pivoting member from one sideof the apparatus, which pivots with respect to a fixed pivot point and afriction-free bearing (for microvibrational displacements) from theother side of the apparatus. The pivoting member pivots in response toforces external to the apparatus which are orthogonal to the principalvibration isolation direction of the apparatus, so that only thecomponent of the external forces, applied from either side of theapparatus, along the principal vibration isolation axis is applied to aninternal isolating load support plate of the apparatus. According tothese embodiments, the friction-free bearing (for microvibrationaldisplacements) is mounted in such a way that only external forces whichare parallel to the principal direction of isolation are passing throughthe bearing and applied to the apparatus.

It is noted that the magnitude of the vibrational waves is verysmall—these are generally referred to as “microvibration”.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

FIG. 1A conceptually illustrates a cross-section of a cross-axisdecoupling device according to an embodiment of the present inventionunder the influence of a force not along the direction of gravitationalforce.

FIG. 1B conceptually illustrates the response of a shear decouplingdevice according to FIG. 1A, under the influence of a cross-axis forcenot orthogonal to the direction of gravitational force.

FIG. 1C shows a schematic representation of a cross-axis decouplingdevice according to an embodiment of the present invention.

FIG. 1D shows a schematic representation of a cross-axis decouplingdevice according to an embodiment of the present invention.

FIG. 2A conceptually illustrates a cross-section of vibration isolationapparatus with cross-axis decoupling devices according to an embodimentof the present invention.

FIG. 2B conceptually illustrates a cross-section of vibration isolationmultiple-axis apparatus with cross-axis decoupling devices according toan embodiment of the present invention.

FIG. 2C illustrates another embodiment with a feedback loop forisolating from vibration orthogonal to the principal vibration isolationdirection.

For simplicity and clarity of illustration, elements shown in thefigures are not necessarily drawn to scale, and the dimensions and/orlocations of some elements may be exaggerated relative to otherelements. In addition, reference numerals may be repeated among thefigures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION

The principles and operation of a cross-axis decoupling vibrationisolator according to various embodiments of the present invention maybe understood with reference to the drawings and the accompanyingdescription.

FIG. 1A conceptually illustrates a cross-section of a cross-axisdecoupling device 100 according to an embodiment of the presentinvention. An isolating mechanism 115 is supported by structure 101,which is attached to shear decoupling, friction free, for microvibrational displacements, bearing 280, and rests on a supportingsurface 260. Vibration force 190, if generated from the surface 260, istranslated through structure 101, to support isolated device payload193, in case vibration force 190 is generated on the payload 193, andtranslated through structure 101 to surface 260. Vibration force 190 isapplied in a principal vibration isolation direction, normal to baseplate of support structure 101. Lower load equalizing springs 102 and103 support an internal load isolating plate 104. Upper equalizingsprings 105 and 106 extend from internal load isolating plate 104 to atop plate of the mechanism 115, which is a continuation of base plate ofsupport structure 101 through the spacing rods 109 and 110 positionedwithin springs 102-105 and 103-106 respectively. The precise position ofisolating plate 104 relative to base plate of support structure 101 isrelated to the compression of springs 102-105 and 103-106, and isadjusted by means of adjustment screws 111 and 112. A pivot point 123 ismounted on internal load isolating plate 104 so that load supportpendulum 121 and internal load isolating plate 104 may freely pivotrelative to one another. A pivot point 125 is mounted at the bottom ofload support pendulum 121, so that pendulum 121 and member 122, which iscontinuation of payload 193, may freely pivot relative to one another.Pivoting support member 122 passes through an opening 116 in topmechanism 115 and is exposed for supporting a payload 193.

The stiffness of springs 102-105, 103-106 is optimally adjusted byscrews 111 and 112 to maximize effectiveness of feedback control loop,based on a inertia motion sensor 132 and a directional actuator 131, incompensation of the dynamic (vibrational) force 190.

In the embodiment described above, pendulum 121 is configured as ahanging pendulum, which by itself is statically stable.

Internal load isolating plate 104 is characterized by having arestricted ability to move only in a principal vibration isolationdirection along spacing rods 109 and 110, and is further isolated fromvibration of support structure 101 or plate 193 by an actuator 131 whichprovides active vibration damping and which is driven according tosignals from an inertial sensor 132 that is associated with internalload isolating plate 104.

FIG. 1B conceptually illustrates the response of cross-axis decouplingdevice 100 under the influence of an external force 160 generated bydevice rested on payload 193. Because of pivot device 121, 122, 123,force 160 is split into force 170 along principal direction ofisolation, and force 180, normal to principal direction of isolation. InFIG. 1B, force 180 is shown causing a displacement of pendulum 121 and apivoting support member 122. The distance of the displacement is denotedas Δx. Load isolating plate 104 and structure 101 however, are isolatedfrom displacing force 180. After displacing force 180 is no longerpresent, pivoting pendulum 121 resiliently returns to its originalshape, as shown in FIG. 1A.

FIG. 1C conceptually illustrates the response of cross-axis decouplingdevice 100 under the influence of an external force 130 generated bysurface 260. Because of bearing 280, force 130 is split into force 140along principal direction of isolation, and force 150 (FIG. 1B), normalto principal direction of isolation. Force 150 is shown causing adisplacement of surface 260. Inertia mass of the Device resting onpayload 193, causing shift of bearing 280, denoted as Δx displacement.Pivot device 121, 122, 123 may also tilt to compensate residual motionΔx Load isolating plate 104 and payload 193, however, are isolated fromdisplacing force 150. After displacing force 150 is no longer present,bearing 280 and pivoting pendulum 121 resiliently returns to itsoriginal shape, as shown in FIG. 1A.

It is once again emphasized that the microvibrational displacementsshown in FIG. 1B and FIG. 1C are greatly exaggerated in dimension forthe purpose of illustration and are not drawn to scale.

FIG. 1D shows a schematic representation of cross-axis decoupling device155 according to an embodiment of the present invention. In thisschematic representation, the internal load isolating plate 104 is shownas a lumped-parameter component 171 having an inertial mass m, restingon an internal plate 172 between equalizing springs 102, 103 andequalizing springs 105, 106, upon which a sensor 173 also rests, with anelectrical connection 174 to an actuator 175. In this representation,internal plate 172 is a “virtual” component, whose physical properties(as a transitional mass m) are embodied in lumped-parameter component171.

Electrical connection 174 also incorporates the lumped parameters ofactive electronics for driving actuator 175 according to signals fromsensor 173. An advantage of having a schematic representation, such asthat of FIG. 1D, is that cross-axis decoupling device 100 can be put toeffective use in more extensive apparatus, and thus analyzed more easilyin terms of lumped parameter m. The schematic representation is alsosimpler to illustrate in complex assemblies.

In this lumped-parameter model: internal plate 172 in contact withsensor 173, which has electrical connection 174 to actuator 175, whichin turn is in contact with internal place 172, together form a feedbackloop for transferring signals from sensor 173 to actuator 175 viaelectrical connection 174, where actuator 175 is responsive to thesignals from sensor 173 to actively contribute to isolating pivotingsupport member 122 from microvibrational displacements affecting bottomsurface 280, upon which the device rests, or transferred from payloadthrough support member 122.

FIG. 2A conceptually illustrates a cross-section of a vibrationisolation apparatus 200 incorporating cross-axis decoupling devices 220and 230 according to an embodiment of the present invention. Bothdevices 220 and 230 are shown in the schematic representation of FIG.1D. Cross-axis decoupling devices 220 and 230 provide independentvibration force compensation, in the principal vibration isolationdirection, on a plate 203, which is resting on the support bases of therespective pivoting support members of cross-axis decoupling devices 220and 230. Plate 203 provides stabilization for the pendulum configurationof the pivoting support members as described previously and illustratedin FIG. 1A. On plate 203 are mounted upper load support springs 212 and214, and dampers 211 and 213 to support a payload platform 207, uponwhich rests a payload object 250 which is to be isolated from thevibrations of a surface 260. In other variation, when vibrationgenerated by payload 250 itself (due to its internal movingcomponents—moving stages, fans, etc.), surface 260 is to be isolated.Dynamic and static forces, applied to spring-damper units 211-212 and213-214, can be different, due to the internal processes in payload 250and its position on plate 207. This means that displacement of thedifferent points on plate 203 also varies significantly. Presence of therespective pivot supports in devices 220 and 230 plays an important rolein decoupling forces applied to the internal load support plates ofthose devices and hence the performance of vibrational compensationcontrol loops of devices 220 and 230.

In an embodiment illustrated in FIG. 2B, cross-axis decoupling devices220 and 230 rest on frictionless (at microvibrational displacements)support bearings located above a lower plate 280. In turn, lower plate280 rests on frictionless (at microvibrational displacements) supportbearings above surface 260. The position of lower plate 280 isstabilized by a cross-axis decoupling device 240, which is oriented atan angle of 90 degrees with respect to the principal vibration isolationdirection. In this particular embodiment, decoupling device 220 has asensor 223 on an internal plate 222, and sensor 223 is connected via anelectrical connection 224 to an actuator 225. (A similar arrangement isprovided for decoupling device 230.) Likewise, decoupling device 240 hasa sensor 243 on an internal plate 242, and sensor 243 is connected viaan electrical connection 244 to an actuator 245, so that the feedbackloop for vibration isolation orthogonal to principal vibration isolationdirection is a local feedback loop internal to device 240.

In another embodiment illustrated in FIG. 2C, a different feedback loopis employed for isolating from vibration that is orthogonal to principalvibration isolation direction. In this embodiment, a sensor 227 incontact with internal plate 222 in device 220 is connected via anelectrical connection 228 to actuator 245 in device 240, so that thefeedback loop for vibration isolation orthogonal to principal vibrationisolation direction 150 is a global feedback loop for apparatus 200.

While the invention has been described with respect to a limited numberof embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made.

1. A vibration isolation apparatus for isolating a payload object fromvibration in a principal direction and for decoupling the payload objectfrom vibration orthogonal to the principal direction, the devicecomprising: a base plate, for contact with a surface that is subject tovibration in the principal direction; at least one decoupling device,each of the at least one decoupling device comprising: at least onelower equalizing spring from the base plate to an internal load supportplate; at least one upper equalizing spring from the internal loadsupport plate to an upper plate; a pivoting load support elementarranged to pivot about a pivot point on a surface of the internal loadsupport plate in a direction substantially orthogonal to the principaldirection of vibration isolation; at least one suspension spring fromthe upper plate to a payload support platform; and at least one damperfrom the upper plate to the payload support platform.
 2. The vibrationisolation apparatus of claim 1, comprising a plurality of decouplingdevices.
 3. The vibration isolation apparatus of claim 2, wherein atleast one of the plurality of decoupling devices has a principaldirection of vibration isolation that is orthogonal to the principaldirection of vibration isolation of at least one other of the pluralityof decoupling devices.
 4. The vibration isolation apparatus of claim 3,wherein the apparatus further comprises: a sensor in contact with aninternal load support plate; an active actuator in contact with aninternal load support plate; and an electrical connection between thesensor and the active actuator, wherein the active actuator isresponsive to a signal from the sensor.
 5. The vibration isolationapparatus of claim 4, wherein the sensor and the actuator are in thesame decoupling device.
 6. The vibration isolation apparatus of claim 4,wherein the sensor and the actuator are in different decoupling devices.7. The vibration isolation apparatus of claim 4, wherein the sensor isin a decoupling device for isolating from vibration in the principaldirection and the actuator is in a decoupling device for isolating fromvibration orthogonal to the principal direction.